High-functionality polyisocyanates containing urethane groups

ABSTRACT

The present invention relates to new, urethane-group-containing polyisocyanates based on aliphatic and/or cycloaliphatic diisocyanates, and to their use.

The present invention relates to new, urethane-group-containingpolyisocyanates based on aliphatic and/or cycloaliphatic diisocyanates,and to their use.

EP 1091991 B1 describes two-component polyurethane mixtures having ahigh-functionality, preferably at least tetrafunctional polyisocyanateas A component and a polyol as B component. The B component may alsocomprise low molecular weight diols to pentaols.

Polyisocyanate and polyol are used only in an NCO:OH ratio of 0.6 to1.4:1, since the mixtures are coating compositions for coatings in whichit is intended that substantially all of the reactive groups should haveundergone reaction after curing.

EP 1497351 B1 describes the preparation of high-functionalitypolyisocyanates by trimerization of a mixture comprising aliphaticdiisocyanates and uretdiones. Alcohols are not present.

EP 1061091 A describes at least difunctional polyisocyanates havingallophanate groups by reaction of polyisocyanates with a monoalcohol andalso, optionally, higher-functionality diols or polyols.

A disadvantage is that by means of an allophanate bonding it is notpossible for more than two polyisocyanates to be linked with oneanother, and hence the functionality of the resultant products islimited.

EP 620237 A2 describes prepolymers formed from diisocyanates andpolyols. Reaction with higher-functionality polyisocyanates is notdisclosed.

A disadvantage of this is that the NCO functionality of the resultantproducts is not higher than the OH functionality of the polyols used.

DE-A 2305695 describes prepolymers formed from diisocyanates and lowmolecular weight polyols having 2 to 4 hydroxyl groups.

Reaction with higher-functionality polyisocyanates is not disclosed.

It was an object of the present invention to provide new polyisocyanateshaving a high functionality for coating materials, particularly fortransparent varnishes and clearcoats, which have a high hardness and/orscratch resistance and/or, in two-component polyurethane coatingmaterials, exhibit accelerated drying and/or improved resistance tosulfuric acid.

This object is achieved by means of high-functionality polyisocyanatescontaining urethane groups and obtainable by

-   -   reacting at least one polyfunctional alcohol (A), having a        functionality which is on average more than 2, the        polyfunctional alcohol (A) being a polyol or a mixture of        polyols,    -   at least one polyisocyanate (B), having a functionality of more        than 2, which contains at least one isocyanurate, biuret,        uretdione and/or allophanate group and is constructed from        aliphatic and/or cycloaliphatic isocyanates,    -   under reaction conditions under which urethane groups are formed        between (A) and (B), with the proviso that    -   the molar ratio of NCO groups to OH groups between (B) and (A)        is at least 3:1.

The polyfunctional alcohol (A) has a functionality of on average morethan 2, preferably at least 2.5, more preferably at least 2.7, and verypreferably at least 3.

The polyfunctional alcohol (A) may be a polyol (A2) or a mixture ofpolyols (A2). It may also be a mixture of at least one diol (A1) with atleast one polyol (A2) having a functionality of at least 3, thus givingthe functionality specified above.

Examples of polyols (A2) are trimethylolbutane, trimethylolpropane,trimethylolethane, pentaerythritol, glycerol, ditrimethylolpropane,dipentaerythritol, sorbitol, mannitol, diglycerol, threitol, erythritol,adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol),maltitol, and isomalt.

Preferred polyols are those having a functionality of between 3 and 4,more preferably those having a functionality of 3.

Preferred polyols are trimethylolpropane, trimethylolethane,pentaerythritol, glycerol, ditrimethylolpropane, and dipentaerythritol,more preferably trimethylolpropane, pentaerythritol, and glycerol, andvery preferably trimethylolpropane and glycerol.

Examples of diols (A1) are aliphatic diols which have two to 20,preferably 2 to 12, carbon atoms, more preferably 1,2-ethanediol,2,2-dimethyl-1,2-ethanediol, 1,2-propanediol, 1,3-propanediol,2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol,2-ethyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol,2-butyl-2-ethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol,1,4-butanediol, 3-methylpentane-1,5-diol, 1,6-hexanediol,2-ethyl-1,3-hexanediol, 2-propyl-1,3-heptanediol, 1,8-octanediol,2,4-diethyloctane-1,3-diol, 1,10-decanediol, or cycloaliphatic diolswhich have six to 20 carbon atoms, preferablybis(4-hydroxycyclohexane)-isopropylidene, tetramethylcyclobutanediol,1,2-, 1,3- or 1,4-cyclohexanediol, cyclooctanediol, norbornanediol,2,2-bis(4-hydroxycyclohexyl)propane, and 1,1-, 1,2-, 1,3-, and1,4-cyclohexane-dimethanol.

Among these the aliphatic diols are preferred, preferably1,2-ethanediol, 1,2-propanediol, 1,3-propanediol,2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,6-hexanediol,2-ethyl-1,3-hexanediol and 2-propyl-1,3-heptanediol, more preferably2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,6-hexanediol,2-ethyl-1,3-hexanediol and 2-propyl-1,3-heptanediol, and very preferably1,4-butanediol and 1,6-hexanediol.

In one preferred embodiment of the present invention the polyfunctionalalcohol (A), preferably the polyol (A2), is used in alkoxylated formand/or in a form esterified with hydroxyalkylcarbonyl, preferably ineither alkoxylated or hydroxyalkylcarbonyl-esterified form.

By an alkoxylated polyol in this context is meant a polyol which isreacted formally on at least one hydroxyl group with one or moreidentical or different alkylene oxides.

Examples of suitable alkylene oxides for such alkoxylation are ethyleneoxide, propylene oxide, n-butylene oxide, isobutylene oxide,vinyloxirane and/or styrene oxide.

The alkylene oxide chain may be composed preferably of ethylene oxide,propylene oxide and/or butylene oxide units. A chain of this kind may becomposed of one species of one alkylene oxide, or of a mixture ofalkylene oxides. Where a mixture is used, the different alkylene oxideunits may be present statistically or as a block or blocks of individualspecies. Preferred alkylene oxide is ethylene oxide, propylene oxide ora mixture thereof, more preferably either ethylene oxide or propyleneoxide, and very preferably ethylene oxide.

The number of alkylene oxide units in the chain is, for example, 1 to,preferably 1 to 5, more preferably 1-4, and more particularly 1-3, basedon the respective hydroxyl groups of the polyol.

Particularly preferred are alkoxylated polyols of the formulae (IIa) to(IIc),

in which

R² is hydrogen or C₁-C₁₈ alkyl,

k, l, m, and q, independently of one another, are each an integer from 1to 10, preferably 1 to 5, more preferably 1 to 4, and very preferably 1to 3, and

each X_(i) for i=1 to k, 1 to l, 1 to m, and 1 to q, independently ofone another, may be selected from the group consisting of —CH₂—CH₂—O—,—CH₂—CH(CH₃)—O—, —CH(CH₃)—CH₂—O—, —CH₂—C(CH₃)₂—O—, —C(CH₃)₂—CH₂—O—,—CH₂—CHVin-O—, —CHVin-CH₂—O—, —CH₂—CHPh-O—, and —CHPh-CH₂—O—, preferablyfrom the group of —CH₂—CH₂—O—, —CH₂—CH(CH₃)—O—, and —CH(CH₃)—CH₂—O—, andmore preferably —CH₂—CH₂—O—,

in which Ph is phenyl and Vin is vinyl.

The compounds in question are preferably acrylates of pentaerythritol,trimethylolethane, trimethylolpropane or glycerol which per hydroxylgroup is singly to pentuply, more preferably singly to quadruply, andvery preferably singly to triply ethoxylated, propoxylated or mixedlyethoxylated and propoxylated, and more particularly exclusivelyethoxylated, or, especially, unalkoxylated.

A hydroxyalkylcarbonyl-esterified form means that the alcohol isesterified with at least one group

in which R¹ is a divalent alkylene radical containing 3 to 7 carbonatoms and n is a positive integer from 1 to 5, preferably 1 to 4, morepreferably 1 to 3.

The alkylene radical R¹ containing 3 to 7, preferably 4 to 6, morepreferably 5 to 6 carbon atoms may be, for example, 1,3-propylene,1,4-butylene, 1,5-pentylene, 1,6-hexylene or 1,5-hexylene, preferably1,4-butylene or 1,5-pentylene, and more preferably 1,5-pentylene.

Where the polyfunctional alcohol (A) is used in the form of a mixture ofpolyols or diols (A1) and polyols (A2), the ratio of these componentsmay be selected arbitrarily, provided that the above-requiredfunctionality of the polyfunctional alcohol (A) is observed.

The ratio of diols (A1) to polyols (A2) is preferably from 10:90 to90:10 (based on the molar amounts of diol and polyol), more preferablyfrom 20:80 to 80:20, very preferably from 30:70 to 70:30, and moreparticularly from 40:60 to 60:40.

The polyisocyanate (B) has a functionality of more than 2, preferably atleast 2.2, more preferably at least 2.4, very preferably at least 2.8,and more particularly at least 3.

The polyisocyanates (B) are constructed from aliphatic and/orcycloaliphatic, preferably either aliphatic or cycloaliphatic,diisocyanates.

The diisocyanates are preferably isocyanates having 4 to 20 C atoms.Examples of customary diisocyanates are aliphatic diisocyanates such astetramethylene diisocyanate, hexamethylenediisocyanate(1,6-diisocyanatohexane), octamethylene diisocyanate,decamethylene diisocyanate, dodecamethylene diisocyanate,tetradecamethylene diisocyanate, derivatives of lysine diisocyanate,trimethylhexane diisocyanate or tetramethylhexane diisocyanate,cycloaliphatic diisocyanates such as 1,4-, 1,3- or1,2-diisocyanatocyclohexane, 4,4′- or2,4′-di(isocyanatocyclohexyl)methane,1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)-cyclohexane(isophoronediisocyanate), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or 2,4- or2,6-diisocyanato-1-methylcyclohexane, and also 3 (or 4),8 (or9)-bis(isocyanatomethyl)tricyclo[5.2.1.0^(2,6)]decane isomer mixtures.

Preferred diisocyanates are 1,6-hexamethylene diisocyanate, isophoronediisocyanate and/or 4,4′- or 2,4′-di(isocyanatocyclohexyl)methane, morepreferably 1,6-hexamethylene diisocyanate and/or isophorone diisocyanateand very preferably 1,6-hexamethylene diisocyanate.

Mixtures of the stated diisocyanates may also be present.

Polyisocyanates contemplated include polyisocyanates containingisocyanurate groups, uretdione diisocyanates, polyisocyanates containingbiuret groups, and polyisocyanates containing urethane and/orallophanate groups, formed from linear or branched C₄-C₂₀ alkylenediisocyanates or cycloaliphatic diisocyanates having a total of 6 to 20C atoms, or mixtures thereof.

The polyisocyanates which can be used preferably have an isocyanategroup (calculated as NCO, molecular weight=42 g/mol) content of 10% to60% by weight, based on the diisocyanate and polyisocyanate (mixture),preferably 12% to 50% by weight, and more preferably 12% to 40% byweight.

Particular preference is given to hexamethylene diisocyanate,1,3-bis(isocyanatomethyl)-cyclohexane, isophorone diisocyanate, anddi(isocyanatocyclohexyl)methane or their polyisocyanates, verypreferably isophorone diisocyanate and hexamethylene diisocyanate ortheir polyisocyanates, and with more particular preference hexamethylenediisocyanate or its polyisocyanates.

Preference extends to

-   -   1) Polyisocyanates containing isocyanurate groups and formed        from aliphatic and/or cycloaliphatic diisocyanates. Particular        preference here is given to the corresponding aliphatic and/or        cycloaliphatic isocyanatoisocyanurates, and more particularly to        those based on hexamethylene diisocyanate and/or isophorone        diisocyanate. The isocyanurates present are more particularly        trisisocyanatoalkyl and/or trisisocyanatocycloalkyl        isocyanurates, which represent cyclic trimers of the        diisocyanates, or mixtures with their higher homologs containing        more than one isocyanurate ring. The isocyanatoisocyanurates        generally have an NCO content of 10% to 30% by weight, more        particularly 15% to 25% by weight, and an average NCO        functionality of 2.6 to 4.5.    -   2) Uretdione diisocyanates having aliphatically and/or        cycloaliphatically attached isocyanate groups, and more        particularly those derived from hexamethylene diisocyanate or        isophorone diisocyanate. Uretdione diisocyanates are cyclic        dimerization products of diisocyanates.        -   The uretdione diisocyanates can be used as            polyisocyanates (B) in a mixture with other polyisocyanates,            more particularly those specified under 1).    -   3) Polyisocyanates containing biuret groups and having        cycloaliphatically or aliphatically attached isocyanate groups,        more particularly tris(6-isocyanatohexyl)biuret or its mixtures        with its higher homologs. These polyisocyanates containing        biuret groups generally have an NCO content of 18% to 22% by        weight and an average NCO functionality of 2.8 to 4.5.    -   4) Polyisocyanates containing urethane and/or allophanate groups        and having aliphatically or cycloaliphatically attached        isocyanate groups, of the kind obtainable, for example, by        reaction of excess amounts of hexamethylene diisocyanate or of        isophorone diisocyanate with monohydric or polyhydric alcohols        such as, for example, methanol, ethanol, isopropanol,        n-propanol, n-butanol, isobutanol, sec-butanol, tert-butanol,        n-hexanol, n-heptanol, n-octanol, n-decanol, n-dodecanol (lauryl        alcohol), 2-ethylhexanol, n-pentanol, stearyl alcohol, cetyl        alcohol, lauryl alcohol, ethylene glycol monomethyl ether,        ethylene glycol monoethyl ether, 1,3-propanediol monomethyl        ether, cyclopentanol, cyclohexanol, cyclooctanol,        cyclododecanol, or mixtures thereof. These polyisocyanates        containing urethane and/or allophanate groups generally have an        NCO content of 12% to 20% by weight and an average NCO        functionality of 2.5 to 4.5.

The polyisocyanates can be used in a mixture, including whereappropriate a mixture with diisocyanates.

For the preparation of the high-functionality, urethane-group-containingpolyisocyanates, polyisocyanate (B) and polyfunctional alcohol (A) arereacted with one another, with or without solvent, under urethanizationconditions.

“Urethanization conditions” here mean that the reaction conditions areselected such that reaction of the isocyanate-group-containing component(B) and the hydroxyl-group-containing component (A) results at leastpartly in urethane groups being formed.

The temperature for this reaction is generally up to 150° C., preferablyup to 120° C., more preferably below 100° C., and very preferably below90° C., and the reaction is usually carried out in the presence of atleast one catalyst that catalyzes the urethanization reaction. Thereaction can alternatively be carried out in the absence of a catalyst.

Generally speaking, the temperature of the reaction ought to be at least20° C., preferably at least 30° C., more preferably at least 40° C., andvery preferably at least 50° C.

Catalysts in this context are those compounds whose presence in areactants mixture produces a higher fraction ofurethane-group-containing reaction products than does the same reactantsmixture in the absence of such compounds under the same reactionconditions.

Examples of these compounds are organic amines, more particularlytertiary aliphatic, cycloaliphatic or aromatic amines, and/orLewis-acidic organometallic compounds. Examples of suitable Lewis-acidicorganometallic compounds include tin compounds, such as tin(II) salts oforganic carboxylic acids, e.g., tin(II) diacetate, tin(II) dioctoate,tin(II) bis(ethylhexanoate), and tin(II) dilaurate, and thedialkyltin(IV) salts of organic carboxylic acids, e.g., dimethyltindiacetate, dibutyltin diacetate, dibutyltin dibutyrate, dibutyltinbis(2-ethylhexanoate), dibutyltin dilaurate, dibutyltin maleate,dioctyltin dilaurate, and dioctyltin diacetate. Zinc(II) salts as wellmay be used, such as zinc(II) dioctoate, for example. Also possible aremetal complexes such as acetylacetonates of iron, of titanium, ofaluminum, of zirconium, of manganese, of nickel, of zinc, and of cobalt.Other metal catalysts are described by Blank et al. in Progress inOrganic Coatings, 1999, vol. 35, pages 19-29.

Preferred Lewis-acidic organometallic compounds are dimethyltindiacetate, dibutyltin dibutyrate, dibutyltin bis(2-ethylhexanoate),dibutyltin dilaurate, dioctyltin dilaurate, zinc(II) dioctoate,zirconium acetylacetonate, and zirconium2,2,6,6-tetramethyl-3,5-heptanedionate.

Additionally, bismuth catalysts and cobalt catalysts, and also cesiumsalts, can be among the catalysts employed. Cesium salts contemplatedinclude those compounds in which the following anions are used: F⁻, Cl⁻,ClO⁻, ClO₃ ⁻, ClO₄ ⁻, Br⁻, I⁻, IO₃ ⁻, CN⁻, OCN⁻, NO₂ ⁻, NO₃ ⁻, HCO₃ ⁻,CO₃ ²⁻, S² ⁻, SH⁻, HSO₃ ⁻, SO₃ ²⁻, HSO₄ ⁻, SO₄ ²⁻, S₂O₂ ²⁻, S₂O₄ ²⁻,S₂O₅ ²⁻, S₂O₆ ²⁻, S₂O₇ ²⁻, S₂O₈ ²⁻, H₂PO₂ ⁻, H₂PO₄ ⁻, HPO₄ ²⁻, PO₄ ³⁻,P₂O₇ ⁴⁻, (OC_(n)H_(2n+1)) ⁻, (C_(n)H_(2n−1)O₂)⁻, (C_(n)H_(2n−3)O₂)⁻, and(C_(n+1)H_(2n−2)O₄)²⁻, where n stands for the numbers 1 to 20.

Preferred in this context are cesium carboxylates in which the anionconforms to the formulae (C_(n)H_(2n−1)O₂)⁻ and (C_(n+1)H_(2n−2)O₄)²⁻,with n being 1 to 20. Particularly preferred cesium salts havemonocarboxylate anions of the general formula (C_(n)H_(2n−1)O₂)⁻, wheren stands for the numbers 1 to 20. Particularly noteworthy in thiscontext are formate, acetate, propionate, hexanoate, and2-ethylhexanoate.

As catalysts it is possible, furthermore, to employ the following:

-   -   organometallic salts of the formula (A)_(n)-R—O—CO—O^(⊖)M^(⊕) as        per U.S. Pat. No. 3,817,939, in which:

A is a hydroxyl group or a hydrogen atom,

n is a number from 1 to 3,

R is a polyfunctional linear or branched, aliphatic or aromatichydrocarbon radical, and

M^(⊕) is a cation, such as an alkali metal cation or a quaternaryammonium cation, such as tetraalkylammonium, and also

-   -   quaternary hydroxyalkylammonium compounds of the formula

R²⁴,R²⁵,R²⁶N^(⊕)—CH₂—CH(OH)—R^(27 ⊖)O—(CO)—R²⁸

as catalyst as per DE-A-26 31 733 (U.S. Pat. No. 4,040,992), with thedefinitions stated therein for the radicals.

Particularly suitable as catalysts for the process are quaternaryammonium salts corresponding to the formula

with

Y^(⊖)=carboxylate (R¹³COO⁻), fluoride (F⁻), carbonate (R¹³O(CO)O⁻) orhydroxide (OH⁻),

of the kind described for Y^(⊖)═OH⁻ in U.S. Pat. No. 4,324,879 and inGerman Laid-Open Specifications 2,806,731 and 2,901,479.

The radical Y^(⊖) is preferably a carboxylate, carbonate or hydroxideand more preferably a carboxylate or hydroxide.

R¹³ therein is hydrogen, C₁ to C₂₀ alkyl, C₆ to C₁₂ aryl or C₇ to C₂₀arylalkyl, each of which may optionally be substituted.

Preferably R¹³ is hydrogen or C₁ to C₈ alkyl.

Preferred quaternary ammonium salts are those in which the radicals R⁹to R¹² are identical or different alkyl groups having 1 to 20,preferably 1 to 4, carbon atoms, which are unsubstituted or substitutedby hydroxyl or phenyl groups.

Two of the radicals R⁹ to R¹² may also form, together with the nitrogenatom and possibly with a further nitrogen or oxygen atom, a heterocyclicfive-, six- or seven-membered ring. In each case the radicals R⁹ to R¹¹may also be ethylene radicals which form, together with the quaternarynitrogen atom and a further tertiary nitrogen atom, a bicyclictriethylenediamine structure, provided that the radical R¹² in that caseis a hydroxyalkyl group having 2 to 4 carbon atoms in which the hydroxylgroup is located preferably in the 2-position relative to the quaternarynitrogen atom. The hydroxy-substituted radical or radicals may alsocomprise other substituents, examples being C₁ to C₄ alkyloxysubstituents.

The ammonium ions in this context may also be part of a mono- ormulti-membered ring system, derived for example from piperazine,morpholine, piperidine, pyrrolidine, quinuclidine ordiazabicyclo[2.2.2]octane.

Examples of groups R⁹ to R¹² containing 1 to 20 carbon atoms are,independently of one another, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl,2,4,4-trimethylpentyl, nonyl, isononyl, decyl, dodecyl, tetradecyl,hexadecyl, octa-decyl, 1,1-dimethylpropyl, 1,1-dimethylbutyl,1,1,3,3-tetramethylbutyl, benzyl, 1-phenylethyl, 2-phenylethyl,α,α-dimethylbenzyl, benzhydryl, p-tolylmethyl, 1-(p-butylphenyl)ethyl,p-chlorobenzyl, 2,4-dichlorobenzyl, p-methoxybenzyl, m-ethoxybenzyl,2-cyanoethyl, 2-cyanopropyl, 2-methoxycarbonylethyl,2-ethoxycarbonylethyl, 2-butoxycarbonylpropyl,1,2-di(methoxycarbonyl)ethyl, 2-methoxyethyl, 2-ethoxyethyl,2-butoxyethyl, diethoxymethyl, diethoxyethyl, chloromethyl,2-chloroethyl, trichloromethyl, trifluoromethyl,1,1-dimethyl-2-chloroethyl, 2-methoxyisopropyl, 2-ethoxyethyl,2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl,6-hydroxyhexyl, 2-hydroxy-2,2-dimethylethyl, 2-phenoxyethyl,2-phenoxypropyl, 3-phenoxypropyl, 4-phenoxybutyl, 6-phenoxyhexyl,2-methoxyethyl, 2-methoxypropyl, 3-methoxypropyl, 4-methoxybutyl,6-methoxyhexyl, 2-ethoxyethyl, 2-ethoxypropyl, 3-ethoxypropyl,4-ethoxybutyl, 6-ethoxyhexyl, phenyl, tolyl, xylyl, α-naphthyl,β-naphthyl, 4-biphenylyl, chlorophenyl, dichlorophenyl, trichlorophenyl,difluorophenyl, methylphenyl, dimethylphenyl, trimethylphenyl,ethylphenyl, diethylphenyl, isopropylphenyl, tert-butylphenyl,dodecylphenyl, methoxyphenyl, dimethoxyphenyl, methylnaphthyl,isopropylnaphthyl, chloronaphthyl, 2,6-dimethylphenyl,2,4,6-trimethylphenyl, 2,6-dimethoxyphenyl, 2,6-dichlorophenyl,cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl, methylcyclopentyl,dimethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl,diethylcyclohexyl, butylcyclohexyl, chlorocyclohexyl,dichlorocyclohexyl, dichlorocyclopentyl, norbornyl or norbornenyl.

The radicals R⁹ to R¹² are preferably, independently of one another, C₁to C₄ alkyl. R¹² may additionally be benzyl or a radical of the formula

in which R¹⁴ and R¹⁵ independently of one another may be hydrogen or C₁to C₄ alkyl.

Particularly preferred radicals R⁹ to R¹² are, independently of oneanother, methyl, ethyl, and n-butyl, and for R¹² additionally benzyl,2-hydroxyethyl, and 2-hydroxypropyl.

For the process of the invention it is possible with preference to usethe following catalysts:

quaternary ammonium hydroxides, preferablyN,N,N-trimethyl-N-benzylammonium hydroxide andN,N,N-trimethyl-N-(2-hydroxypropyl)ammonium hydroxide, as per DE-A-38 06276.

Hydroxyalkyl-substituted quaternary ammonium hydroxides as per EP-A-10589 (U.S. Pat. No. 4,324,879).

Organometallic salts of the formula (A)_(n)-R—O—CO—O^(⊖)M^(⊕) as perU.S. Pat. No. 3,817,939, in which A is a hydroxyl group or a hydrogenatom, n is a number from 1 to 3, R is a polyfunctional linear orbranched, aliphatic or aromatic hydrocarbon radical, and M is a cationof a strong base, e.g., an alkali metal cation or a quaternary ammoniumcation, such as tetraalkylammonium.

Preferred catalysts are zinc(II) salts, and of these particularly zincacetylacetonate.

Additionally preferred is dibutyltin dilaurate.

Depending on its activity, the catalyst is used normally in amounts of0.001 to 10 mol % based on isocyanate groups employed, preferably 0.5 to8, more preferably 1 to 7, and very preferably 2 to 5 mol %.

The polyisocyanate (B) is used in an at least threefold excess of theNCO groups, based on the hydroxyl groups in the polyfunctional alcohol(A), preferably in an at least 4-fold excess, more preferably in an atleast 5-fold excess, and very preferably in an at least 6-fold excess.

The unreacted portion of polyisocyanate (B) may either be separated offor, preferably, remain in the reaction mixture.

The reaction is carried out preferably without solvent, but may also becarried out in the presence of at least one solvent. Similarly, thereaction mixture obtained may be formulated in a solvent after the endof the reaction.

Solvents which can be used are those which do not have groups that arereactive toward isocyanate groups, and in which the polyisocyanates aresoluble to an extent of at least 10%, preferably at least 25%, morepreferably at least 50%, very preferably at least 75%, more particularlyat least 90%, and especially at least 95% by weight.

Examples of solvents of this kind are aromatic hydrocarbons (includingalkylated benzenes and naphthalenes) and/or (cyclo)aliphatichydrocarbons, and mixtures thereof, chlorinated hydrocarbons, ketones,esters, alkoxylated alkanoic acid alkyl esters, ethers, or mixtures ofthe solvents.

Preferred aromatic hydrocarbon mixtures are those which comprisepredominantly aromatic C₇ to C₁₄ hydrocarbons and may span a boilingrange from 110 to 300° C., particular preference being given to toluene,o-, m- or p-xylene, trimethylbenzene isomers, tetramethylbenzeneisomers, ethylbenzene, cumene, tetrahydronaphthalene, and mixturescomprising these.

Examples thereof are the Solvesso® grades from ExxonMobil Chemical,especially Solvesso® 100 (CAS no. 64742-95-6, predominantly C₉ and C₁₀aromatics, boiling range about 154-178° C.), 150 (boiling range about182-207° C.), and 200 (CAS no. 64742-94-5), and the Shellsol® gradesfrom Shell, Caromax® (e.g., Caromax® 18) from Petrochem Carless, andHydrosol from DHC (e.g., as Hydrosol® A 170). Hydrocarbon mixturescomprising paraffins, cycloparaffins, and aromatics are also availablecommercially under the designations Kristalloel (examples beingKristalloel 30, boiling range about 158-198° C., or Kristalloel 60: CASno. 64742-82-1), white spirit (for example, likewise CAS no. 64742-82-1)or solvent naphtha (light: boiling range about 155-180° C., heavy:boiling range about 225-300° C.). The aromatics content of hydrocarbonmixtures of this kind is generally more than 90%, preferably more than95%, more preferably more than 98%, and very preferably more than 99% byweight. It may make sense to use hydrocarbon mixtures having aparticularly reduced naphthalene content.

Examples of (cyclo)aliphatic hydrocarbons include decalin, alkylateddecalin, and isomer mixtures of linear or branched alkanes and/orcycloalkanes. The aliphatic hydrocarbons content is generally less than5%, preferably less than 2.5%, and more preferably less than 1% byweight.

Examples of esters include n-butyl acetate, ethyl acetate,1-methoxyprop-2-yl acetate, and 2-methoxyethyl acetate.

Examples of ethers are tetrahydrofuran (THF), dioxane, and the dimethyl,diethyl or di-n-butyl ethers of ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, dipropylene glycol or tripropyleneglycol.

Examples of ketones are acetone, diethyl ketone, ethyl methyl ketone,isobutyl methyl ketone, methyl amyl ketone, and tert-butyl methylketone.

In one preferred embodiment of the present invention thehigh-functionality polyisocyanates of the invention are formulated witha solvent. A preferred solvent is n-butyl acetate.

The concentration of the polyisocyanate of the invention in the solutionought to be at least 50%, preferably at least 60%, and more preferablyat least 70% by weight.

The high-functionality polyisocyanates of the invention, containingurethane groups, generally have an NCO functionality of more than 2,preferably at least 3, more preferably at least 4, very preferably atleast 5, and more particularly more than 6.

The high-functionality polyisocyanates of the invention, containingurethane groups, generally have a number-average molecular weight Mn of1000 to 20 000, preferably of 1200 to 10 000, and more preferably of1500 to 5000 g/mol and a weight-average molecular weight Mw of 1000 to50 000 and preferably of 1500 to 30 000. The molecular weights can bedetermined by gel permeation chromatography with a suitable polymerstandard and tetrahydrofuran or dimethylformamide as eluent.

The high-functionality, urethane-group-containing polyisocyanates of theinvention find application for example in two-component polyurethanecoating materials featuring at least one component comprising at leasttwo isocyanate-reactive groups (binder). For this purpose thehigh-functionality, urethane-group-containing polyisocyanates of theinvention may be used alone or in a mixture with other polyisocyanates(C) as a crosslinker component.

Such other polyisocyanates (C) are obtainable by oligomerization ofmonomeric isocyanates.

The monomeric isocyanates used for this may be aromatic, aliphatic orcycloaliphatic, preferably aliphatic or cycloaliphatic, which isreferred to for short in this text as (cyclo)aliphatic; aliphaticisocyanates are particularly preferred.

Aromatic isocyanates are those which comprise at least one aromatic ringsystem, in other words not only purely aromatic compounds but alsoaraliphatic compounds.

Cycloaliphatic isocyanates are those which comprise at least onecycloaliphatic ring system.

Aliphatic isocyanates are those which comprise exclusively linear orbranched chains, i.e., acyclic compounds.

The monomeric isocyanates are preferably diisocyanates, which carryprecisely two isocyanate groups. They can, however, in principle also bemonoisocyanates, having one isocyanate group.

In principle, higher isocyanates having on average more than 2isocyanate groups are also contemplated. Suitability therefor ispossessed for example by triisocyanates such as triisocyanatononane,2,4,6-triisocyanatotoluene, triphenylmethane triisocyanate or2,4,4′-triisocyanatodiphenyl ether, or the mixtures of diisocyanates,triisocyanates, and higher polyisocyanates that are obtained, forexample, by phosgenation of corresponding aniline/formaldehydecondensates and represent methylene-bridged polyphenyl polyisocyanates.

These monomeric isocyanates do not contain any substantial products ofreaction of the isocyanate groups with themselves.

The monomeric isocyanates are preferably isocyanates having 4 to 20 Catoms. Examples of typical diisocyanates are aliphatic diisocyanatessuch as tetramethylene diisocyanate, pentamethylene 1,5-diisocyanate,hexamethylene diisocyanate(1,6-diisocyanatohexane), octamethylenediisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate,tetradecamethylene diisocyanate, derivatives of lysine diisocyanate,trimethylhexane diisocyanate or tetramethylhexane diisocyanate,cycloaliphatic diisocyanates such as 1,4-, 1,3- or1,2-diisocyanatocyclohexane, 4,4′- or2,4′-di(isocyanatocyclohexyl)methane,1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexane(isophoronediisocyanate), 1,3- or 1,4-bis-(isocyanatomethyl)cyclohexane or 2,4-, or2,6-diisocyanato-1-methylcyclohexane, and also 3 (or 4), 8 (or9)-bis(isocyanatomethyl)tricyclo[5.2.1.0^(2,6)]decane isomer mixtures,and also aromatic diisocyanates such as tolylene 2,4- or2,6-diisocyanate and the isomer mixtures thereof, m- or p-xylylenediisocyanate, 2,4′- or 4,4′-diisocyanatodiphenylmethane and the isomermixtures thereof, phenylene 1,3- or 1,4-diisocyanate, 1-chlorophenylene2,4-diisocyanate, naphthylene 1,5-diisocyanate, diphenylene4,4′-diisocyanate, 4,4′-diisocyanato-3,3′-dimethylbiphenyl,3-methyldiphenylmethane 4,4′-diisocyanate, tetramethylxylylenediisocyanate, 1,4-diisocyanatobenzene or diphenyl ether4,4′-diisocyanate.

Particular preference is given to hexamethylene 1,6-diisocyanate,1,3-bis(isocyanatomethyl)-cyclohexane, isophorone diisocyanate, and4,4′- or 2,4′-di(isocyanatocyclohexyl)methane, very particularpreference to isophorone diisocyanate and hexamethylene1,6-diisocyanate, and especial preference to hexamethylene1,6-diisocyanate.

Mixtures of said isocyanates may also be present.

Isophorone diisocyanate is usually in the form of a mixture,specifically a mixture of the cis and trans isomers, generally in aproportion of about 60:40 to 80:20 (w/w), preferably in a proportion ofabout 70:30 to 75:25, and more preferably in a proportion ofapproximately 75:25.

Dicyclohexylmethane 4,4′-diisocyanate may likewise be in the form of amixture of the different cis and trans isomers.

It is possible to use not only those diisocyanates obtained byphosgenating the corresponding amines but also those prepared withoutthe use of phosgene, i.e., by phosgene-free processes. According toEP-A-0 126 299 (U.S. Pat. No. 4,596,678), EP-A-126 300 (U.S. Pat. No.4,596,679), and EP-A-355 443 (U.S. Pat. No. 5,087,739), for example,(cyclo)aliphatic diisocyanates, such as hexamethylene 1,6-diisocyanate(HDI), isomeric aliphatic diisocyanates having 6 carbon atoms in thealkylene radical, 4,4′- or 2,4′-di(isocyanatocyclohexyl)methane, and1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane(isophoronediisocyanate or IPDI) can be prepared by reacting the (cyclo)aliphaticdiamines with, for example, urea and alcohols to give (cyclo)aliphaticbiscarbamic esters and subjecting said esters to thermal cleavage intothe corresponding diisocyanates and alcohols. The synthesis takes placeusually continuously in a circulation process and in the presence, ifdesired, of N-unsubstituted carbamic esters, dialkyl carbonates, andother by-products recycled from the reaction process. Diisocyanatesobtained in this way generally contain a very low or even unmeasurablefraction of chlorinated compounds, which is advantageous, for example,in applications in the electronics industry.

In one embodiment the isocyanates used have a total hydrolyzablechlorine content of less than 200 ppm, preferably of less than 120 ppm,more preferably less than 80 ppm, very preferably less than 50 ppm, inparticular less than 15 ppm, and especially less than 10 ppm. This canbe measured by means, for example, of ASTM specification D4663-98. Ofcourse, though, monomeric isocyanates having a higher chlorine contentcan also be used, of up to 500 ppm, for example.

It will be appreciated that it is also possible to employ mixtures ofthose monomeric isocyanates which have been obtained by reacting the(cyclo)aliphatic diamines with, for example, urea and alcohols andcleaving the resulting (cyclo)aliphatic biscarbamic esters, with thosediisocyanates which have been obtained by phosgenating the correspondingamines.

The polyisocyanates (C) which can be formed by oligomerizing themonomeric isocyanates are generally characterized as follows:

The average NCO functionality of such compounds is in general at least1.8 and can be up to 8, preferably 2 to 5, and more preferably 2.4 to 4.

The isocyanate group content after oligomerization, calculated as NCO=42g/mol, is generally from 5% to 25% by weight unless otherwise specified.

The polyisocyanates (C) are preferably compounds as follows:

-   -   1) Polyisocyanates containing isocyanurate groups and derived        from aromatic, aliphatic and/or cycloaliphatic diisocyanates.        Particular preference is given in this context to the        corresponding aliphatic and/or cycloaliphatic        isocyanatoisocyanurates and in particular to those based on        hexamethylene diisocyanate and isophorone diisocyanate. The        isocyanurates present are, in particular, trisisocyanatoalkyl        and/or trisisocyanatocycloalkyl isocyanurates, which constitute        cyclic trimers of the diisocyanates, or are mixtures with their        higher homologs containing more than one isocyanurate ring. The        isocyanatoisocyanurates generally have an NCO content of 10% to        30% by weight, in particular 15% to 25% by weight, and an        average NCO functionality of 2.6 to 8.    -   2) Polyisocyanates containing uretdione groups and having        aromatically, aliphatically and/or cycloaliphatically attached        isocyanate groups, preferably aliphatically and/or        cycloaliphatically attached, and in particular those derived        from hexamethylene diisocyanate or isophorone diisocyanate.        Uretdione diisocyanates are cyclic dimerization products of        diisocyanates.        -   The polyisocyanates containing uretdione groups are obtained            in the context of this invention as a mixture with other            polyisocyanates, more particularly those specified under 1).            For this purpose the diisocyanates can be reacted under            reaction conditions under which not only uretdione groups            but also the other polyisocyanates are formed, or the            uretdione groups are formed first of all and are            subsequently reacted to give the other polyisocyanates, or            the diisocyanates are first reacted to give the other            polyisocyanates, which are subsequently reacted to give            products containing uretdione groups.    -   3) Polyisocyanates containing biuret groups and having        aromatically, cycloaliphatically or aliphatically attached,        preferably cycloaliphatically or aliphatically attached,        isocyanate groups, especially tris(6-isocyanatohexyl)biuret or        its mixtures with its higher homologs. These polyisocyanates        containing biuret groups generally have an NCO content of 18% to        22% by weight and an average NCO functionality of 2.8 to 6.    -   4) Polyisocyanates containing urethane and/or allophanate groups        and having aromatically, aliphatically or cycloaliphatically        attached, preferably aliphatically or cycloaliphatically        attached, isocyanate groups, such as may be obtained, for        example, by reacting excess amounts of diisocyanate, such as of        hexamethylene diisocyanate or of isophorone diisocyanate, with        mono- or polyhydric alcohols. These polyisocyanates containing        urethane and/or allophanate groups generally have an NCO content        of 12% to 24% by weight and an average NCO functionality of 2.5        to 4.5. Polyisocyanates of this kind containing urethane and/or        allophanate groups may be prepared without catalyst or,        preferably, in the presence of catalysts, such as ammonium        carboxylates or ammonium hydroxides, for example, or        allophanatization catalysts, such as Zn(II) compounds, for        example, in each case in the presence of monohydric, dihydric or        polyhydric, preferably monohydric, alcohols.    -   5) Polyisocyanates comprising oxadiazinetrione groups, derived        preferably from hexamethylene diisocyanate or isophorone        diisocyanate. Polyisocyanates of this kind comprising        oxadiazinetrione groups are accessible from diisocyanate and        carbon dioxide.    -   6) Polyisocyanates comprising iminooxadiazinedione groups,        derived preferably from hexamethylene diisocyanate or isophorone        diisocyanate. Polyisocyanates of this kind comprising        iminooxadiazinedione groups are preparable from diisocyanates by        means of specific catalysts.    -   7) Uretonimine-modified polyisocyanates.    -   8) Carbodiimide-modified polyisocyanates.    -   9) Hyperbranched polyisocyanates, of the kind known for example        from DE-A1 10013186 or DE-A1 10013187.    -   10) Polyurethane-polyisocyanate prepolymers, from di- and/or        polyisocyanates with alcohols.    -   11) Polyurea-polyisocyanate prepolymers.    -   12) The polyisocyanates 1)-11), preferably 1), 3), 4), and 6),        can be converted, following their preparation, into        polyisocyanates containing biuret groups or urethane/allophanate        groups and having aromatically, cycloaliphatically or        aliphatically attached, preferably (cyclo)aliphatically        attached, isocyanate groups. The formation of biuret groups, for        example, is accomplished by addition of water or by reaction        with amines. The formation of urethane and/or allophanate groups        is accomplished by reaction with monohydric, dihydric or        polyhydric, preferably monohydric, alcohols, in the presence if        desired of suitable catalysts. These polyisocyanates containing        biuret or urethane/allophanate groups generally have an NCO        content of 18% to 22% by weight and an average NCO functionality        of 2.8 to 6.    -   13) Hydrophilically modified polyisocyanates, i.e.,        polyisocyanates which as well as the groups described under 1-12        also comprise groups which result formally from addition of        molecules containing NCO-reactive groups and hydrophilizing        groups to the isocyanate groups of the above molecules. The        latter groups are nonionic groups such as alkylpolyethylene        oxide and/or ionic groups derived from phosphoric acid,        phosphonic acid, sulfuric acid or sulfonic acid, and/or their        salts.    -   14) Modified polyisocyanates for dual cure applications, i.e.,        polyisocyanates which as well as the groups described under 1-12        also comprise groups resulting formally from addition of        molecules containing NCO-reactive groups and UV-crosslinkable or        actinic-radiation-crosslinkable groups to the isocyanate groups        of the above molecules. These molecules are, for example,        hydroxyalkyl(meth)acrylates and other hydroxyvinyl compounds.

The diisocyanates or polyisocyanates recited above may also be presentat least partly in blocked form.

Classes of compounds used for blocking are described in D. A. Wicks, Z.W. Wicks, Progress in Organic Coatings, 36, 148-172 (1999), 41, 1-83(2001) and also 43, 131-140 (2001).

Examples of classes of compounds used for blocking are phenols,imidazoles, triazoles, pyrazoles, oximes, N-hydroxyimides,hydroxybenzoic esters, secondary amines, lactams, CH— acidic cyclicketones, malonic esters or alkyl acetoacetates.

In one preferred embodiment of the present invention the polyisocyanate(C) is selected from the group consisting of isocyanurates, biurets,urethanes, and allophanates, preferably from the group consisting ofisocyanurates, urethanes, and allophanates, more preferably from thegroup consisting of isocyanurates and allophanates; in particular it isa polyisocyanate containing isocyanurate groups.

In one particularly preferred embodiment the polyisocyanate (C)encompasses polyisocyanates comprising isocyanurate groups and obtainedfrom 1,6-hexamethylene diisocyanate.

In one further particularly preferred embodiment the polyisocyanateencompasses a mixture of polyisocyanates comprising isocyanurate groupsand obtained from 1,6-hexamethylene diisocyanate and from isophoronediisocyanate.

In one particularly preferred embodiment the polyisocyanate (C) is amixture comprising low-viscosity polyisocyanates, preferablypolyisocyanates comprising isocyanurate groups, having a viscosity of600-1500 mPa*s, more particularly below 1200 mPa*s, low-viscosityurethanes and/or allophanates having a viscosity of 200-1600 mPa*s, moreparticularly 600-1500 mPa*s, and/or polyisocyanates comprisingiminooxadiazinedione groups.

In this specification, unless noted otherwise, the viscosity is reportedat 23° C. in accordance with DIN EN ISO 3219/A.3 in a cone/plate systemwith a shear rate of 1000 s⁻¹.

The high-functionality, urethane-group-containing polyisocyanates of theinvention may if desired be used in a mixture with other polyisocyanates(C), as crosslinker components, with at least one binder in polyurethanecoating materials.

Generally speaking, for polyisocyanate compositions, in other words thesum of the compounds containing isocyanate groups,

50% to 100% by weight of the high-functionality,urethane-group-containing polyisocyanates of the invention are used,preferably 50% to 90% by weight, and more preferably 60% to 80% byweight, and

0% to 50% by weight of other polyisocyanates (C), preferably 10% to 50%,more preferably 20% to 40% by weight,

with the proviso that the sum is always 100% by weight.

The binders may be, for example, polyacrylate polyols, polyesterpolyols, polyether polyols, polyurethane polyols; polyurea polyols;polyester-polyacrylate polyols; polyester-polyurethane polyols;polyurethane-polyacrylate polyols, polyurethane-modified alkyd resins;fatty-acid-modified polyester-polyurethane polyols, copolymers withallyl ethers, graft polymers of the stated groups of compounds having,for example, different glass transition temperatures, and also mixturesof the stated binders. Preference is given to polyacrylate polyols,polyester polyols, and polyether polyols.

Preferred OH numbers, measured in accordance with DIN 53240-2, are40-350 mg KOH/g resin solids for polyesters, preferably 80-180 mg KOH/gresin solids, and 15-250 mg KOH/g resin solids for polyacrylateols,preferably 80-160 mg KOH/g.

Additionally the binders may have an acid number in accordance with DINEN ISO 3682 of up to 200 mg KOH/g, preferably up to 150 and morepreferably up to 100 mg KOH/g.

Polyacrylate polyols preferably have a molecular weight M_(n) of atleast 1000, more preferably at least 2000, and very preferably at least5000 g/mol. The molecular weight M_(n) may in principle have no upperlimit, and may preferably be up to 200 000, more preferably up to 100000, very preferably up to 80 000, and more particularly up to 50 000g/mol.

The latter may be, for example, monoesters of α,β-unsaturated carboxylicacids, such as acrylic acid, methacrylic acid (identified for short inthis specification as “(meth)acrylic acid”), with diols or polyols whichhave preferably 2 to 20 C atoms and at least two hydroxyl groups, suchas ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propyleneglycol, 1,3-propylene glycol, 1,1-dimethyl-1,2-ethanediol, dipropyleneglycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol,tripropylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol,neopentyl glycol hydroxypivalate, 2-ethyl-1,3-propanediol,2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol,1,6-hexanediol, 2-methyl-1,5-pentanediol, 2-ethyl-1,4-butanediol,2-ethyl-1,3-hexanediol, 2,4-diethyloctane-1,3-diol,2,2-bis(4-hydroxycyclohexyl)propane, 1,1-, 1,2-, 1,3- and1,4-bis(hydroxymethyl)cyclohexane, 1,2-, 1,3- or 1,4-cyclohexanediol,glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane,pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol,mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol(lyxitol), xylitol, dulcitol (galactitol), maltitol, isomalt, polyTHFwith a molar weight between 162 and 4500, preferably 250 to 2000,poly-1,3-propanediol or polypropylene glycol with a molar weight between134 and 2000, or polyethylene glycol with a molar weight between 238 and2000.

Preference is given to 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, 2- or 3-hydroxypropyl acrylate, 1,4-butanediolmonoacrylate or 3-(acryloyloxy)-2-hydroxypropyl acrylate, and particularpreference to 2-hydroxyethyl acrylate and/or 2-hydroxyethylmethacrylate.

The hydroxyl-bearing monomers are used in the copolymerization in amixture with other polymerizable monomers, preferably free-radicallypolymerizable monomers, preferably those composed to an extent of morethan 50% by weight of C₁-C₂₀, preferably C₁ to C₄ alkyl(meth)acrylate,(meth)acrylic acid, vinylaromatics having up to 20 C atoms, vinyl estersof carboxylic acids comprising up to 20 C atoms, vinyl halides,nonaromatic hydrocarbons having 4 to 8 C atoms and 1 or 2 double bonds,unsaturated nitriles, and mixtures thereof. Particular preference isgiven to the polymers composed to an extent of more than 60% by weightof C₁-C₁₀ alkyl(meth)acrylates, styrene and its derivatives,vinylimidazole or mixtures thereof.

In addition the polymers may contain hydroxy-functional monomerscorresponding to the above hydroxyl group content and, if desired,further monomers, examples being (meth)acrylic acid glycidyl epoxyesters, ethylenically unsaturated acids, more particularly carboxylicacids, acid anhydrides or acid amides.

Further polymers are, for example, polyesterols, as are obtainable bycondensing polycarboxylic acids, especially dicarboxylic acids, withpolyols, especially diols. In order to ensure a polyester polyolfunctionality that is appropriate for the polymerization, use is alsomade in part of triols, tetrols, etc, and also triacids etc.

Polyester polyols are known for example from Ullmanns Encyklopädie dertechnischen Chemie, 4th edition, volume 19, pp. 62 to 65. It ispreferred to use polyester polyols which are obtained by reactingdihydric alcohols with dibasic carboxylic acids. In lieu of the freepolycarboxylic acids it is also possible to use the correspondingpolycarboxylic anhydrides or corresponding polycarboxylic esters oflower alcohols or mixtures thereof to prepare the polyester polyols. Thepolycarboxylic acids may be aliphatic, cycloaliphatic, aromatic orheterocyclic and may if desired be substituted, by halogen atoms forexample, and/or unsaturated. Examples thereof that may be mentionedinclude the following:

Oxalic acid, maleic acid, fumaric acid, succinic acid, glutaric acid,adipic acid, sebacic acid, dodecanedioic acid, o-phthalic acid,isophthalic acid, terephthalic acid, trimellitic acid, azelaic acid,1,4-cyclohexanedicarboxylic acid or tetrahydrophthalic acid, subericacid, azelaic acid, phthalic anhydride, tetrahydrophthalic anhydride,hexahydrophthalic anhydride, tetrachloro-phthalic anhydride,endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleicanhydride, dimeric fatty acids, their isomers and hydrogenationproducts, and also esterifiable derivatives, such as anhydrides ordialkyl esters, C₁-C₄ alkyl esters for example, preferably methyl, ethylor n-butyl esters, of the stated acids are employed. Preference is givento dicarboxylic acids of the general formula HOOC—(CH₂)_(y)—COOH, wherey is a number from 1 to 20, preferably an even number from 2 to 20, andmore preferably succinic acid, adipic acid, sebacic acid, anddodecanedicarboxylic acid.

Suitable polyhydric alcohols for preparing the polyesterols include1,2-propanediol, ethylene glycol, 2,2-dimethyl-1,2-ethanediol,1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol,3-methylpentane-1,5-diol, 2-ethylhexane-1,3-diol,2,4-diethyloctane-1,3-diol, 1,6-hexanediol, polyTHF having a molar massof between 162 and 4500, preferably 250 to 2000, poly-1,3-propanediolhaving a molar mass between 134 and 1178, poly-1,2-propanediol having amolar mass between 134 and 898, polyethylene glycol having a molar massbetween 106 and 458, neopentyl glycol, neopentyl glycol hydroxypivalate,2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol,2,2-bis(4-hydroxycyclohexyl)propane, 1,1-, 1,2-, 1,3- and1,4-cyclohexane-dimethanol, 1,2-, 1,3- or 1,4-cyclohexanediol,trimethylolbutane, trimethylolpropane, trimethylolethane, neopentylglycol, pentaerythritol, glycerol, ditrimethylolpropane,dipentaerythritol, sorbitol, mannitol, diglycerol, threitol, erythritol,adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol),maltitol or isomalt, which if desired may have been alkoxylated asdescribed above.

Preferred alcohols are those of the general formula HO—(CH₂)_(x)—OH,where x is a number from 1 to 20, preferably an even number from 2 to20. Preferred are ethylene glycol, butane-1,4-diol, hexane-1,6-diol,octane-1,8-diol and dodecane-1,12-diol. Additionally preferred isneopentyl glycol.

Also suitable, furthermore, are polycarbonate diols of the kindobtainable, for example, by reacting phosgene with an excess of the lowmolecular mass alcohols specified as synthesis components for thepolyester polyols.

Also suitable are lactone-based polyester diols, which are homopolymersor copolymers of lactones, preferably hydroxy-terminated adducts oflactones with suitable difunctional starter molecules. Suitable lactonesare preferably those which derive from compounds of the general formulaHO—(CH₂)_(z)—COOH, where z is a number from 1 to 20 and where one H atomof a methylene unit may also have been substituted by a C₁ to C₄ alkylradical. Examples are ε-caprolactone, β-propiolactone,gamma-butyrolactone and/or methyl-ε-caprolactone, 4-hydroxybenzoic acid,6-hydroxy-2-naphthoic acid or pivalolactone, and mixtures thereof.Examples of suitable starter components include the low molecular massdihydric alcohols specified above as a synthesis component for thepolyester polyols. The corresponding polymers of ε-caprolactone areparticularly preferred. Lower polyester diols or polyether diols as wellcan be used as starters for preparing the lactone polymers. In lieu ofthe polymers of lactones it is also possible to use the corresponding,chemically equivalent polycondensates of the hydroxycarboxylic acidscorresponding to the lactones.

Also suitable as polymers, furthermore, are polyetherols, which areprepared by addition reaction of ethylene oxide, propylene oxide orbutylene oxide with H-active components. Polycondensates of butanediolare also suitable.

In addition it is possible to use hydroxy-functional carboxylic acids,such as dimethylolpropionic acid or dimethylolbutanoic acid, forexample.

The polymers can of course also be compounds containing primary orsecondary amino groups.

For the purpose of preparing the polyurethane coating materials,polyisocyanate composition and binder are mixed with one another in amolar ratio of isocyanate groups to isocyanate-reactive groups of 0.1:1to 10:1, preferably 0.2:1 to 5:1, more preferably 0.3:1 to 3:1, verypreferably 0.5:1 to 2:1, more particularly 0.8:1 to 1.2:1, andespecially 0.9:1 to 1.1:1, it being possible if desired to mix infurther, typical coatings constituents, and the resulting mixture isapplied to the substrate.

Subsequently the coating-material mixture is cured under suitableconditions. Depending on application, this may take place, for example,at 100 to 140° C., in the case for example of coating materials in OEMapplications, or in a lower temperature range of 20 to 80° C., forexample.

Depending on temperature, this usually takes not more than 12 hours,preferably up to 8 hours, more preferably up to 6, very preferably up to4, and in particular up to 3 hours.

It is additionally possible for coating compositions to comprise 0% to10% by weight of at least one UV stabilizer.

Suitable stabilizers comprise typical UV absorbers such as oxanilides,triazines, and benzotriazole (the latter available as Tinuvin® gradesfrom Ciba-Spezialitätenchemie), and benzophenones.

They may further comprise 0% to 5% by weight of suitable free-radicalscavengers, examples being sterically hindered amines such as2,2,6,6-tetramethylpiperidine, 2,6-di-tert-butylpiperidine orderivatives thereof, e.g., bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate.

Furthermore, coating compositions may further comprise 0% to 10% byweight of further, typical coatings additives.

Further, typical coatings additives that can be used include, forexample, antioxidants, activators (accelerants), fillers, pigments,dyes, antistatic agents, flame retardants, thickeners, thixotropicagents, surface-active agents, viscosity modifiers, plasticizers orchelating agents.

Suitable thickeners, in addition to free-radically (co)polymerized(co)polymers, include typical organic and inorganic thickeners such ashydroxymethylcellulose or bentonite.

Chelating agents which can be used include, for example,ethylenediamineacetic acid and salts thereof, and also β-diketones.

Suitable fillers comprise silicates, examples being silicates obtainableby hydrolysis of silicon tetrachloride, such as Aerosil® from Degussa,siliceous earth, talc, aluminum silicates, magnesium silicates, calciumcarbonates, etc.

The substrates are coated by typical methods known to the skilledworker, with at least one coating composition being applied in thedesired thickness to the substrate to be coated, and any volatileconstituents of the coating composition being removed, if appropriatewith heating. This operation may if desired be repeated one or moretimes. Application to the substrate may take place in a known way, asfor example by spraying, troweling, knifecoating, brushing, rolling,rollercoating, flowcoating, laminating, injection backmolding orcoextruding.

The thickness of a film of this kind for curing may be from 0.1 μm up toseveral mm, preferably from 1 to 2000 μm, more preferably 5 to 200 μm,very preferably from 5 to 60 μm (based on the coating material in thestate in which the solvent has been removed from the coating material).

Additionally provided by the present invention are substrates coatedwith a coating material comprising the urethane-group-containingpolyisocyanates of the invention.

Polyurethane coating materials of this kind are especially suitable forapplications requiring particularly high application reliability,exterior weathering resistance, optical qualities, solvent resistance,chemical resistance, and water resistance.

The two-component coating compositions and coating formulations obtainedare in principle suitable for coating substrates such as wood, woodveneer, paper, cardboard, paperboard, textile, film, leather, nonwoven,plastics surfaces, glass, ceramic, mineral building materials, such asmolded cement blocks and fiber-cement slabs, or metals, which in eachcase may optionally have been precoated or pretreated. With particularpreference, however, they are suitable for the coating of plasticssurfaces and metallic substrates.

These coating compositions are used preferably as clearcoat, basecoat,and topcoat(s), primers and surfacers, and in particular they aresuitable, on account of their high scratch resistance, as topcoatmaterial, preferably as clearcoat material, more particularly incoatings on (large) vehicles and aircraft, and in automobile finishes asOEM and refinish.

It is an advantage of the urethane-group-containing polyisocyanates ofthe invention that in clearcoats they produce high scratch resistance inconjunction with good elasticity. Moreover, the products of theinvention usually result in a relatively low viscosity.

EXAMPLES

Polyisocyanate A:

Basonat® HI 100 from BASF SE, HDI isocyanurate having an NCO content of22.2% and a viscosity of 3500 mPa*s at 23° C., functionality of about3.4.

Polyisocyanate B:

Basonat® LR 9046 from BASF SE, HDI isocyanurate having an NCO content of23.7% and a viscosity of 1350 mPa*s at 23° C., functionality of about3.2.

Trifunctional Alcohol A:

Trifunctional polyethylene oxide prepared with potassium hydroxidecatalysis, starting from trimethylolpropane, and having an OH number of600 mg KOH/g (to DIN 53240) and a molecular weight of 277 g/mol.

Trifunctional Alcohol B:

Trifunctional polypropylene oxide prepared with potassium hydroxidecatalysis, starting from trimethylolpropane, and having an OH number of546 (to DIN 53240) and a molecular weight of 308 g/mol.

Trifunctional Alcohol C:

Polycaprolactone prepared in the presence of butyltintris(2-ethylhexanoate), starting from trimethylolpropane, by reactionwith 3 equivalents of caprolactone, and having an OH number of 319 (toDIN 53240) and a molecular weight of 527.8 g/mol.

Hazen Color Number:

Method for determining the yellowing of technical liquids to DIN ISO6271. An acidic solution of potassium hexachloroplatinate is used as thestandard.

Comparative Example 1

Basonat® HI 100 from BASF SE: HDI isocyanurate having an NCO content of22.2% and a viscosity of 2800 mPa*s at 23° C.

Comparative Example 2

Desmodur® N3790 from Bayer AG: HDI isocyanurate (90% in butyl acetate),having an NCO content of 17.8% and a viscosity of 2150 mPa*s at 23° C.

Example 1

300.00 g (0.5236 mol) of polyisocyanate A, 11.70 g (0.084 mol) oftrimethylolpropane in 133.6 g of butyl acetate were mixed. The solutionis hazy at room temperature and has an NCO content of 14.9%. Thesolution becomes transparent when the temperature is raised from roomtemperature to 60° C. The mixture was reacted with addition ofdibutyltin dilaurate as catalyst. After 2 hours at 60° C., the NCOcontent was 12.3%. The batch was then cooled and filtered through SeitzT5500 filters. The product has a viscosity of 550 mPas at 23° C. and acolor number of 14 Hazen.

Example 2

294.60 g (0.53 mol) of polyisocyanate A, 25.00 g (0.084 mol) oftrifunctional alcohol A in 137.0 g of butyl acetate were mixed. Thesolution is transparent at room temperature and has an NCO content of14.4%. The mixture was reacted with addition of dibutyltin dilaurate ascatalyst. After 1 hour at 80° C., the NCO content was 11.5%. The batchwas then cooled and filtered through Seitz T5500 filters. Thecorresponding product had a viscosity of 470 mPas at 23° C. and a colornumber of 60 Hazen.

Example 3

300.00 g (0.524 mol) of polyisocyanate A, 26.86 g (0.084 mol) oftrifunctional alcohol B in 140.08 g of butyl acetate were mixed. Thesolution was transparent at room temperature and had an NCO content of14.1%. The mixture was reacted with addition of dibutyltin dilaurate ascatalyst. After 2 hours at 60° C., the NCO content was 10.4%. The batchwas then cooled and filtered through Seitz T5500 filters. Thecorresponding product had a viscosity of 500 mPas at 23° C. and a colornumber of 18 Hazen.

Example 4

230.4 g (0.42 mol) of polyisocyanate A, 25.0 g (0.047 mol) oftrifunctional alcohol C in 75.0 g of butyl acetate were mixed. Thesolution was transparent at room temperature. The mixture was reactedwith addition of dibutyltin dilaurate as catalyst. After 1.5 hours at60° C., the NCO content was 11.2%. The batch was then cooled andfiltered through Seitz T5500 filters. The corresponding product had aviscosity of 760 mPas at 23° C. and a color number of 10 Hazen.

Example 5

350.0 g (0.65 mol) of polyisocyanate B and 5.0 g (0.050 mol) of glycerolwere mixed in 152.1 g of butyl acetate. The solution was transparent atroom temperature. The mixture was reacted with addition of dibutyltindilaurate as catalyst. After 2 hours at 80° C., the NCO content was14.4%. The batch was then cooled and filtered through Seitz T5500filters. The product obtained had a viscosity of 70 mPas at 23° C. and acolor number of 20 Hazen.

Performance Testing:

The inventive and comparative polyisocyanates were mixed withacrylic-acid-free, hydroxy-functional polyacrylate polyols (Joncryl®922, BASF; solids content=80% in butyl acetate; OH number=143 mg KOH/g,corresponding to a stoichiometric NCO/OH ratio of 1:1) and were adjustedwith butyl acetate to an application viscosity of 20 s (DIN 53 211, cup4 mm efflux nozzle). Using a drawing frame, coatings with a wet filmthickness of 200 μm were applied to metal panels. The resultantclearcoats were flashed off at room temperature for 10 minutes and, fordetermining the scratch resistance and acid resistance, were cured at60° C. over a period of 30 minutes. Prior to the tests the coating filmswere stored for 24 h at 23±2° C. and 50±10% humidity.

Test Methods:

The gel time is considered to be the time between coating-materialformulation and complete gelling of the coating material.

For determining the drying rate of the coating-material surface, thecoating material, after application, was contacted at regular intervalswith a cotton pad. The test is ended when cotton fibers no longer adhereto the coating-material surface.

The pendulum hardness was determined by the method of König (EN ISO1522).

The cross-cut was determined in accordance with EN ISO 2409. The ratingsin that test are between 0 (very good adhesive strength) and 5 (verypoor adhesive strength).

For determining the scratch resistance of the coating material, thesurface is subjected to scratching using a scouring pad containingcorundum particles, under a weight of 500 g. The damage is determinedvia the gloss value of the coating material. The reflow is determined byheating, at the temperature indicated in the table and for the timeindicated in the table, after scratching via 50 double rubs.

The sulfuric acid resistance was tested (etch test) in accordance withEN ISO 2812-1 (method 3) in the temperature range of 35-75° C.:

Using a pipette, a 25 μm drop of 1% strength sulfuric acid was appliedto a coating material, cured at a predetermined temperature (30 minutesat 80 or 130° C.) on a gradient oven panel, and this metal panel washeated in the gradient oven at 35-75° C. for 30 minutes. The panel wassubsequently washed with water and dried. The parameter reported is thelowest temperature at which initial etching on the coating material wasdiscernible.

The temperature of the curing of the coating material is identified inthe table by 80° C. or 130° C.

n.d. stands for measurement values not determined.

Comp. example 1 Comp. example 2 Example 1 Example 2 Example 3 Example 4Example 5 Cotton test (min) 260 210 100 75 48 70 210 Etch test 80° C., 0h [° C.] <30 <30 42 39 40 38 43 after 24 h [° C.] <30 <30 42 38 40 38 43Scratch resistance 80° C.; 20° [%] 94 93 97 97 96 95 95 Scratchresistance 80° C.; 60° [%] 100 100 101 101 101 102 102 10 double rubs;20° [%] 2 8 13 33 34 16 n.d. 10 double rubs; 60° [%] 7 21 32 51 58 36n.d. 50 double rubs; 20° [%] 1 1 2 2 2 2 n.d. 50 double rubs; 60° [%] 56 9 8 8 10 n.d. Scratch resistance 130° C.; 20° [%] 96 89 97 96 96 95n.d. Scratch resistance 130° C.; 60° [%] 102 101 102 101 101 103 101 10double rubs; 20° [%] 8 19 20 22 23 13 n.d. 10 double rubs; 60° [%] 25 5150 52 56 46 n.d. 50 double rubs; 20° [%] 2 5 4 5 5 5 n.d. 50 doublerubs; 60° [%] 6 15 17 18 18 18 n.d. Pendulum damping 80° C. 38 49 80 7080 72 59 Pendulum damping 130° C. 62 73 118 111 115 107 103

1. A high-functionality polyisocyanate, comprising urethane groups andobtained by: reacting (a) at least one polyfunctional alcohol (A),having a functionality which is on average more than 2, wherein thepolyfunctional alcohol (A) is a polyol or a mixture of polyols; (b) atleast one polyisocyanate (B), having a functionality of more than 2,which comprises at least one selected from the group consisting ofisocyanurate, biuret, uretdione, and allophanate group and comprises atleast one selected from the group consisting of an aliphatic isocyanateand a cycloaliphatic isocyanate, under reaction conditions under whichurethane groups are formed between (A) and (B), with the proviso that amolar ratio of NCO groups to OH groups between (B) and (A) is at least3:1.
 2. The high-functionality polyisocyanate of claim 1, wherein thepolyisocyanate (B) comprises at least one polyisocyanate comprising atleast one isocyanurate group, are based on 1,6-hexamethylenediisocyanate, and having a viscosity of 600-3000 mPa*s.
 3. Thehigh-functionality polyisocyanate of claim 1, wherein the polyfunctionalalcohol (A) comprises at least one polyol selected from the groupconsisting of trimethylolpropane, glycerol, pentaerythritol, andditrimethylolpropane.
 4. The high-functionality polyisocyanate of claim3, wherein the polyol is alkoxylated.
 5. The high-functionalitypolyisocyanate of claim 3, wherein the polyol is esterified with atleast one group

wherein R¹ is a divalent alkylene radical comprising 3 to 7 carbonatoms, and n is a positive integer from 1 to
 5. 6. Thehigh-functionality polyisocyanate of claim 1, wherein the polyfunctionalalcohol (A) is a mixture which comprises at least one diol selected fromthe group consisting of 1,2-ethanediol, 1,2-propanediol,1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol,2-ethyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol,1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol,2-ethyl-1,3-hexanediol, 2-propyl-1,3-heptanediol, and 1,8-octanediol. 7.A two-component coating composition, comprising the high functionalitypolyisocyanate of claim
 1. 8. A two-component coating composition,comprising: at least one high-functionality polyisocyanate of claim 1;at least one compound having at least 2 groups that are reactive towardisocyanate groups; and optionally, at least one selected from the groupconsisting of a solvent, a pigment, an additive, and a thickener.
 9. Aprocess for preparing a polyurethane coating material, comprising:reacting the high-functionality polyisocyanate of claim 1 with at leastone binder which comprises isocyanate-reactive groups.
 10. A process forpreparing a polyurethane coating material, comprising: reacting thehigh-functionality polyisocyanate of claim 1 with at least one binderselected from the group consisting of a polyacrylate polyol, a polyesterpolyol, a polyether polyol, a polyurethane polyol, a polyurea polyol, apolyetherol, a polycarbonate, a polyesterpolyacrylate polyol, apolyesterpolyurethane polyol, a polyurethanepolyacrylate polyol, apolyurethane-modified alkyd resin, a fatty-acid-modifiedpolyesterpolyurethane polyol, a copolymer with at least one allyl ether,and a copolymer, and a graft polymer from at least one of the compoundsstated.
 11. A coating material, comprising the high-functionalitypolyisocyanate of claim
 1. 12. A refinish-coating system, wood-coatingsystem, vehicle coating system, comprising the high-functionalitypolyisocyanate of claim
 1. 13. An adhesive or sealant, comprising thehigh-functionality polyisocyanate of claim
 1. 14. The coating materialof claim 11, which is a polyurethane coating material.
 15. A method ofcuring a coating material, the method comprising heating a coatingmaterial comprising the high-functionality polyisocyanate of claim 1.16. The high-functionality polyisocyanate of claim 1, wherein thepolyisocyanate (B) comprises a biuret group.
 17. The high-functionalitypolyisocyanate of claim 1, wherein the polyisocyanate (B) comprises auretdione group.
 18. The high-functionality polyisocyanate of claim 1,wherein the polyisocyanate (B) comprises a allophanate group.
 19. Thehigh-functionality polyisocyanate of claim 1, wherein the polyfunctionalalcohol (A) comprises trimethylolpropane.
 20. The high-functionalitypolyisocyanate of claim 1, wherein the polyfunctional alcohol (A)comprises glycerol.